10 Tips

for
HEIRLOOM TOMATOES

Heirloom tomatoes are a favorite crop of many growers, bringing both a premium price and customers in search of old-fashioned tomato flavor. Growing heirloom tomatoes can be tricky, though, often requiring more labor and producing lower yields than modern tomato varieties.

The biggest concern with heirloom tomato production is disease. Unlike modern hybrids, which have generally had disease resistance bred into them, most old-fashioned varieties have minimal resistance. As a result, heirlooms may not produce for as long a time period as disease-resistant varieties. And if they lose a significant amount of foliage to disease, they won't taste as good as they should because it's the leaves that convert sunlight into sugars and other flavor compounds. Preventing disease, then, is paramount for commercial production of heirloom tomatoes.

In this article, we recommend 10 strategies that can help make heirloom tomatoes profitable for your farm.

The single most effective cultivation practice with heirloom tomatoes is to use grafted plants, with the heirloom variety grafted onto a vigorous, disease-resistant rootstock.

Grafted heirlooms can produce yields 30–50% greater than nongrafted heirlooms. Grafting reduces the risk of soilborne diseases, and many growers feel that it leads to an overall vigor that helps the plants resist foliar diseases as well.

Heirloom tomatoes do better when grown in high tunnels, where their foliage stays dry. Many tomato diseases thrive in moist conditions, including late blight, leaf mold, Botrytis and Alternaria.

Because most heirlooms form big, vigorous plants, they require a tall tunnel and a strong trellising system. Most greenhouse and high-tunnel tomatoes are pruned to a single leader, and trained to a string that can be lowered later in the season, so that fruits remain accessible from the ground. Grafted heirlooms can, however, be trained to a double leader, so fewer plants are required (making grafting more cost-effective). To accomplish this, all suckers need to be pruned except the one directly below the first flower cluster. That sucker will grow into a second main stem. Labor-saving innovations such as the Rollerhook® and Tomahook simplify the lower-and-lean process.

Because most heirloom tomatoes are vigorous growers, they do need to be pruned more often. Pruning (also called "suckering") is important because removing suckers provides better air circulation, which helps prevent foliar diseases. Pruning also encourages larger fruit production at the top of the plant.

Adopt a methodical approach to choosing which heirloom varieties you grow. Trial a range of varieties and keep records, to pinpoint those that perform best in your conditions. As a quick reference on color, days-to-maturity, size, and texture, use our interactive Heirloom Tomato Variety Comparison Chart.

In All About Tomatoes, we also give an overview of important selection criteria. Andrew Mefferd, Johnny's tomato trial technician, offers additional advice on heirlooms in How to Choose Tomato Varieties, an article published in Growing for Market.

Most heirloom varieties have thin skin, which enhances eating quality but also makes the fruit prone to splitting on the vine. Being careful not to overwater can help to reduce the number of splits.

Plus, when tomatoes receive more water than needed, the excess is directed into the fruits, which has the effect of diluting flavor.

By providing whatever water is required intermittently, in several smaller irrigations rather than all at once, you can alleviate splitting and gain better flavor. Carrying a portable moisture meter is a convenient way to obtain quick, accurate soil-moisture readings.

Newer, heirloom-like varieties have been carefully bred to produce fruit with all the exquisite flavor and eating quality of true heirlooms, but from plants that have better overall vigor and disease resistance. The favorable yield and from these newer "tomato hybrids from heirloom genetics" goes a long way toward justifying the slightly higher seed cost: they simply produce a lot more without being prone to keeling over to disease the way heirlooms sometimes do.

Margold resembles Striped German, an heirloom revered for both its sweetness and its beautiful appearance.

Both Marnero and Margold faithfully (and remarkably) preserve the fruit quality of the heirlooms they imitate, but they also incorporate plant habits and disease resistances that allow for much greater yields than true heirlooms, which tend to die off prematurely in greenhouse conditions.

Finally, there are many imitations of the classic French heirloom Marmande on the market today, but our trials have showed us that Marbonne offers by far the best flavor of the bunch, along with excellent vigor and disease resistance for field production or protected culture.

To grow the best heirloom tomatoes, you will want to keep abreast of new developments, experiment a little, and refine your practices over time. Be sure to review best cultural practices for tomatoes before you start. ATTRA's free publication on Organic Tomato Production offers excellent, comprehensive advice on all facets of growing tomatoes.

With careful attention to best production practices — especially proactive disease prevention — heirloom tomatoes may become a successful, profitable crop for you, as well as a big hit with your customers.